208 pregnant women from the recruiting centers will be enrolled as follow: Women eligible to participate, prior informed consent, will be randomized to 2 capsules twice daily before breakfast and before dinner from randomization until delivery. The boxes will be given to the patients coded and blinded to investigators and participants, and will contain either the active ingredient (VIVOMIXX®, a mixture of 112 billion of eight strains for each capsule, namely Streptococcus thermophilus, bifidobacteria (B. breve, B. longum, B. infantis) and lactobacilli (L. paracasei, L. acidophilus, L. delbrueckii subsp bulgaricus, L. plantarum) or placebo.